In mobile radio communications, the quality of a radio link over which data is transferred varies over time, due to changes in the distance between the mobile station and the radio base station, changes in the interference from other radio links, changes in the reflection pattern of the radio waves caused for example by passing cars, etc. Such changes in the radio conditions will influence different channels differently. Hence, in order to ensure a good quality connection between the mobile terminal and the radio base station, the quality of the radio link should preferably be monitored, and actions should be taken if the monitoring shows that the quality of the radio link is unacceptable or can be improved. Such actions could include re-scheduling the radio link to another channel, and/or adapting the transmission format, such as the modulation scheme and channel coding parameters, to the new conditions.
When allocating radio resources to radio links within a cell, it is important to take into account interference of radio links in other cells which are transmitting at the same frequency.
In U.S. Pat. No. 5,956,642, a method and system of adaptive channel allocation in a multi-carrier, multi-slot system is provided, by which co-channel interference between cells is reduced. In the disclosed method and system, an initial subset of M channels is chosen from a larger set of N channels that are available for communication on each separate link of the multi-carrier, multi-slot system. The subset of M channels is used to carry communications on the link. As communications take place on the link, the channel-over-interference level (C/I) of the channels within the subset of M channels, and the interference (I) level of all N available channels is periodically measured. During communications on the link, the system determines from the C/I and I measurements if at least one more preferred unused channel which would give better signal reception on the link than at least one channel of the set of M is available in the cell within which the link exists. If it is determined that at least one more preferred unused channel exists, the system reconfigures the subset of M channels to include the at least one unused channel.